U.S. patent application number 15/931339 was filed with the patent office on 2020-08-27 for water-soluble or water-swellable polymers as water loss reducers in cement slurries.
This patent application is currently assigned to Clariant International Ltd.. The applicant listed for this patent is Clariant International Ltd.. Invention is credited to Claudia DIEMEL, Dirk FISCHER, Christoph KAYSER, Michael SCHAFER, Jurgen TONHAUSER.
Application Number | 20200270506 15/931339 |
Document ID | / |
Family ID | 1000004824407 |
Filed Date | 2020-08-27 |
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United States Patent
Application |
20200270506 |
Kind Code |
A1 |
FISCHER; Dirk ; et
al. |
August 27, 2020 |
Water-Soluble Or Water-Swellable Polymers As Water Loss Reducers In
Cement Slurries
Abstract
This invention relates to water-soluble or water-swellable
polymers, containing a) 25-35 mol. % of one or more recurrent
structural units of formula (1), where R.sup.1 and R.sup.2
represent hydrogen, methyl or ethyl, A represents a linear or
branched C.sub.1-C.sub.12-alkylene, and Q.sup.+stands for
NH.sub.4.sup.+, Li.sup.+, Na.sup.+, K.sup.+, 1/2 Ca.sup.++, 1/2
Mg.sup.++, 1/2 Zn.sup.++, 1/3 Al.sup.+++, or organic ammonium ions
of the formula [HNR.sup.5R.sup.6R.sup.7].sup.+, b) 3 to 8 mol. % of
one or more recurrent structural units of formula (2), where
R.sup.1 represents hydrogen, methyl, or ethyl, X.sup.+stands for
H.sup.+, NH.sub.4.sup.+, Li.sup.+, Na.sup.+, K.sup.+, 1/2
Ca.sup.++, 1/2 Mg.sup.++, 1/2 Zn.sup.++, 1/3 Al.sup.+++, or organic
ammonium ions of the formula [HNR.sup.5R.sup.6R.sup.7].sup.+, B is
a linear or branched alkylene group with 1 to 6 carbon atoms, and n
is a whole number between 0 and 5, and c) 57 to 72 mol. % of a
(meth)acrylamide. ##STR00001## ##STR00002##
Inventors: |
FISCHER; Dirk; (Hahnheim,
DE) ; KAYSER; Christoph; (Mainz, DE) ; DIEMEL;
Claudia; (Gelnhausen, DE) ; TONHAUSER; Jurgen;
(Oestrich-Winkel, DE) ; SCHAFER; Michael;
(Grundau-Rothenbergen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Clariant International Ltd. |
Muttenz |
|
CH |
|
|
Assignee: |
Clariant International Ltd.
Muttenz
CH
|
Family ID: |
1000004824407 |
Appl. No.: |
15/931339 |
Filed: |
May 13, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15737205 |
Dec 15, 2017 |
|
|
|
PCT/EP2016/062289 |
May 31, 2016 |
|
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15931339 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L 3/02 20130101; C04B
24/383 20130101; C04B 28/02 20130101; C08L 3/08 20130101; C04B
2103/46 20130101; C04B 24/2688 20130101; C08L 33/26 20130101; C08F
220/56 20130101; C04B 24/165 20130101; C04B 40/0042 20130101; C08L
3/04 20130101; C04B 2103/0053 20130101; C09K 8/487 20130101; C04B
2103/0051 20130101; C08F 2800/10 20130101 |
International
Class: |
C09K 8/487 20060101
C09K008/487; C08F 220/56 20060101 C08F220/56; C08L 33/26 20060101
C08L033/26; C08L 3/02 20060101 C08L003/02; C08L 3/08 20060101
C08L003/08; C04B 40/00 20060101 C04B040/00; C04B 28/02 20060101
C04B028/02; C04B 24/16 20060101 C04B024/16; C04B 24/26 20060101
C04B024/26; C04B 24/38 20060101 C04B024/38; C08L 3/04 20060101
C08L003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 17, 2015 |
EP |
15001797.8 |
Claims
1-24. (canceled)
25. A method for cementing deep wells using a cement slurry,
wherein the cement slurry comprises a water-soluble or
water-swellable polymer having a k value of 100 to 300, measured in
0.5% by weight solution in distilled water, containing a) 25-35 mol
% of one or more recurrent structural units of the formula (1)
##STR00007## in which R.sup.1, R.sup.2 are hydrogen, methyl or
ethyl, A is linear or branched C.sub.1-C.sub.12-alkylene, and
Q.sup.+ is H.sup.+, NH.sub.4.sup.+, Li.sup.+, Na.sup.+, K.sup.+,
1/2 Ca.sup.++, 1/2 Mg.sup.++, 1/2 Zn.sup.++, 1/3 Al.sup.+++,
organic ammonium ions of the formula
[HNR.sup.6R.sup.6R.sup.7].sup.+ where R.sup.5, R.sup.6 and R.sup.7
may each independently be hydrogen, a linear or branched alkyl
group having 1 to 22 carbon atoms, a linear or branched, mono- or
polyunsaturated alkenyl group having 2 to 22 carbon atoms, a
C.sub.6-C.sub.22-alkylamidopropyl group, a linear monohydroxyalkyl
group having 2 to 10 carbon atoms or a linear or branched
dihydroxyalkyl group having 3 to 10 carbon atoms, and where at
least one of the R.sup.5, R.sup.6 and R.sup.7 radicals is not
hydrogen, or mixtures of these ions, b) 3 to 8 mol % of one or more
recurrent structural units of the formula (2) ##STR00008## in which
R.sup.1 is hydrogen, methyl or ethyl, X.sup.+ is H.sup.+,
NH.sub.4.sup.+, Li.sup.+, Na.sup.+, K.sup.+, 1/2 Ca.sup.++, 1/2
Mg.sup.++, 1/2 Zn.sup.++, 1/3 Al.sup.+++, organic ammonium ions of
the formula [HNR.sup.5R.sup.6R.sup.7].sup.+ where R.sup.5, R.sup.6
and R.sup.7 may each independently be hydrogen, a linear or
branched alkyl group having 1 to 22 carbon atoms, a linear or
branched, mono- or polyunsaturated alkenyl group having 2 to 22
carbon atoms, a C.sub.6-C.sub.22-alkylamidopropyl group, a linear
monohydroxyalkyl group having 2 to 10 carbon atoms or a linear or
branched dihydroxyalkyl group having 3 to 10 carbon atoms, and
where at least one of the R.sup.5, R.sup.6 and R.sup.7 radicals is
not hydrogen, or mixtures of these ions, B is a chemical bond, or a
linear or branched alkylene group having 1 to 6 carbon atoms, and n
is an integer from 0 to 5, and c) 57 to 72 mol % of one or more
recurrent structural units of the formula (3) ##STR00009## in which
R.sup.1 is hydrogen, methyl or ethyl, and R.sup.3 and R.sup.4 are
each independently hydrogen, methyl, ethyl, n-propyl, isopropyl or
butyl.
26. The method as claimed in claim 25, wherein the structural units
of the formula (1) are derived from monomers from the group
consisting of acryloyldimethyltaurate,
acryloyl-1,1-dimethyl-2-methyltaurate, acryloyltaurate,
acryloyl-N-methyltaurate.
27. The method as claimed in claim 25, wherein the structural units
of the formula (2) are derived from methacrylic acid, acrylic acid,
carboxyethyl acrylate or higher oligomers of the formula (2) in
which n is an integer of 2 or more.
28. The method as claimed in claim 25, wherein the structural units
of the formula (3) are derived from acrylamide, N-methylacrylamide,
N-ethylacrylamide, N,N-diethylmethacrylamide,
N,N-diethylacrylamide, N,N--dimethylmethacrylamide,
N,N-dimethylacrylamide, N-isopropylacrylamide,
N-tert-butylacrylamide and N-butylacrylamide.
29. The method as claimed in claim 25, wherein Q.sup.+ in formula
(1) is selected from the group consisting of NH.sub.4.sup.+,
Na.sup.+ and mixtures of these ions and X.sup.+ in formula (2) is
selected from the group consisting of H.sup.+, NH.sub.4.sup.+,
Na.sup.+ and mixtures of these ions.
30. The method as claimed in claim 25, which contains structural
units of a) 27.5 to 32.5 mol % of acryloyldimethyltaurate, b) 4.5
to 7.5 mol % of acrylic acid, and c) 60 to 68 mol % of
acrylamide.
31. The method as claimed in claim 25, in which the neutralization
level of the structural units of the formula (1) is 95 to 100 mol
%.
32. The method as claimed in claim 25, in which n=0 in at least 70%
of all the structural units of the formula (2).
33. The method as claimed in claim 25, in which n is 0 or 1.
34. The method as claimed in claim 25, in which formula (3) is
derived from acrylamide.
35. The method as claimed in claim 25, containing 27.5 to 32.5 mol
% of the structural units (1), 4.5 to 7.5 mol % of the structural
units (2) and 60 to 68 mol % of the structural units (3).
36. The method as claimed in claim 25, in which formula (1)
represents acryloyldimethyltaurate, formula (2) represents acrylic
acid and formula (3) represents acrylamide.
37. The method as claimed in claim 25, wherein the polymer is
prepared by subjecting monomers from which the structural units of
components a) to c) derive to free-radical precipitation
polymerization in a polar solvent, and the monomers are optionally
neutralized prior to the polymerization, or the polymer is
optionally neutralized after the polymerization, with ammonia,
ammonium carbonate or organic amines or an Li.sup.+--, Na.sup.+--,
K.sup.+--, Ca.sup.++--, Mg.sup.++--, Zn.sup.++-- or Al.sup.+++--
containing base.
38. The method as claimed in claim 37, wherein the polar solvent
has a boiling point of 60 to 110.degree. C.
39. The method as claimed in claim 37, wherein the polar solvent is
a solvent mixture of d) water and e) one or more further polar
solvents.
40. The method as claimed in claim 37, wherein the polar solvent
comprises methanol, ethanol, 1-propanol, 2-propanol,
2-methyl-2-propanol, 1-butanol, 2-butanol, dimethyl ketone, diethyl
ketone, pentan-2-one, butanone, tetrahydropyran, tetrahydrofuran,
2-methyltetrahydrofuran, 1,3-dioxane or 1,4-dioxane.
41. The method as claimed in claim 37, in which the polar solvent
comprises 2-methylpropan-2-ol.
42. The method as claimed in claim 37, wherein the polar solvent
comprises 1% to 5% by weight of water.
43. The method as claimed in claim 37, wherein 27.5 to 32.5 mol %
of acryloyldimethyltaurate, and 4.5 to 7.5 mol % of acrylic acid,
60 to 68 mol % of acrylamide is subjected to free-radical
precipitation polymerization in a mixture of 1 to 8% by weight of
water and 92% to 99% by weight of 2-methylpropan-2-ol, and the
monomers prior to the polymerization or the polymer after the
polymerization are/is optionally neutralized with ammonia, ammonium
carbonate, sodium hydroxide, sodium carbonate.
Description
[0001] The present invention relates to water-soluble or
water-swellable polymers based on acryl-, methacryl- or
ethacrylamidoalkylsulfonic acid or salts thereof and carboxyalkyl
acrylate, methacrylate or ethacrylate or oligomers of these
carboxyl compounds, and acrylamides or alkylacrylamides, to a
process for preparing these polymers and to the use thereof as
water loss reducers in cement slurries for cementing deep wells for
reducing the water loss at the wellbore wall (fluid loss
additives).
[0002] In deep wells for developing mineral oil and natural gas
deposits, the use of cement slurries has long been known. Once the
wellbore has reached a certain depth, what are called feed tubes
are introduced into the wellbore. For this purpose, the feed tubes
have to be fixed, meaning that a cement slurry is pumped into the
cavity between the rock and the feed tubes and hardens to give a
solid rock. The cement rock which forms has to be impermeable to
gases and liquids, in order that no gas and/or oil can flow out of
the reservoir rock into other sections or up to the surface. High
demands are made on the cement slurry to be pumped. It should have
good pumpability, i.e. minimum viscosity, and nevertheless not
exhibit any separation. The release of water from the cement slurry
to the porous rock during the pumping operation should be low, in
order that no thick filtercakes form at the wellbore wall, which
would increase the pump pressure because of the annular space
constriction to such a high degree that the porous rock breaks up.
Moreover, the cement slurry, in the case of excessive water
release, would not set optimally and would become permeable to gas
and oil. On the other hand, the cement shell which forms in the
annular space must attain sufficient strength very quickly, and no
shrinkage, which leads to flow channels for gas, oil and water, may
occur in the course of setting. Optimal adjustment of the
properties of the cement slurry is possible only by means of
additives. The most important additives are retardants,
accelerators, dispersants and water loss reducers.
[0003] Effective water loss reducers used in practice for cement
and gypsum slurries are a wide variety of different polymers,
copolymers and combinations thereof. The first effective products,
which are still being used even now, were cellulose ethers based on
hydroxyethyl cellulose and carboxymethyl hydroxyethyl cellulose.
Owing to thermal instability, these lose efficiency at wellbore
temperatures above 100.degree. C. (212.degree. F.). If the
temperature rises to about 120.degree. C. to 150.degree. C.,
thermal breakdown of these biogenic substances commences. As a
result, many different fully synthetic thermally stabilized
polymers have been developed and are still being used nowadays at
the different temperatures and salinities of the cement slurry.
[0004] Polymers as additives for reducing the water loss from
cement slurries are well known in the literature, although many
have very limited activity in the temperature range between
30.degree. C. (86.degree. F.) and 200.degree. C. (392.degree.
F.).
[0005] U.S. Pat. No. 2,614,998 describes the use of partly
hydrolyzed polyacrylamide (polyacrylamide-co-acrylic acid) as water
loss-reducing polymer. However, these polymers can lead to
significant delays in the setting time of the cement and show only
low efficacy at high temperatures.
[0006] U.S. Pat. Nos. 2,865,876, 2,905,565 and 3,052,628 describe
the use of sulfonated polymers as additives. The polymers and
copolymers described therein differ distinctly in terms of
composition from the copolymers of the invention and have gained no
technical significance at all.
[0007] U.S. Pat. No. 5,472,051 describes copolymers of
acryloyldimethyltaurate and acrylic acid having molecular weights
of less than 5000 g/mol. However, these polymers can lead to severe
delays in the setting time of the cement and, because of the
molecular weight, show high water losses at high temperatures.
[0008] WO-99026991 and EP-1045869 teach copolymers of
acryloyldimethyltaurate and acrylamide, but these polymers, in
direct comparison with the copolymers of the invention, exhibit
poorer performance properties below a temperature of 50.degree. C.
(122.degree. F.) (comparative example 1).
[0009] U.S. Pat. No. 4,015,991 describes a polymer prepared by
polymerization of acryloyldimethyltaurate and acrylamide in water,
wherein at least 20% of the acrylamide units have to be hydrolyzed
subsequently to acrylic acid or a salt of acrylic acid. The
copolymer described in the examples of U.S. Pat. No. 4,015,991 has
formed through the polymerization of 116.4 g (0.56 mol) of
acryloyldimethyltaurate and 14.7 g (0.207 mol) of acrylamide in
water. After at least 20% of the acrylamide units have been
hydrolyzed to acrylic acid, U.S. Pat. No. 4,015,991 claims the
following copolymer:
##STR00003##
where x is 73.8 mol % y is max. 21.8 mol % z is at least 4.4 mol %,
depending on y.
[0010] However, the disadvantage of this polymer is an unwanted
influence on the cement properties (reduction in hardened cement
strength) and the delaying effect on the solidification of the
cement. A further problem is the restricted temperature range for
use as a water loss-reducing polymer. At 176.7.degree. C.
(350.degree. F.), it is demonstrably inactive (comparative examples
5 and 6). U.S. Pat. No. 4,015,991 showed that it is not possible by
aqueous polymerization of acryloyldimethyltaurate and acrylamide
without a hydrolysis step to produce any copolymer suitable for
application purposes.
[0011] EP-0116671 discloses the introduction of 5%-60% by weight of
vinylamides (e.g. N-vinylmethylacetamide) into
acryloyldimethyltaurate-containing polymers. In this way, the
high-temperature range of the application was significantly
extended. However, these polymers have poorer performance
properties at temperatures below a temperature of 50.degree. C.
(122.degree. F.).
[0012] U.S. Pat. No. 5,025,040 describes copolymers of
acryloyldimethyltaurate, acrylamide and at least 20%
N-vinylimidazole.
[0013] U.S. Pat. No. 4,931,489 discloses copolymers of substituted
acrylamides and N-vinylimidazoles, without the use of
acryloyldimethyltaurate.
[0014] EP-0217608, U.S. Pat. No. 4,555,269 and EP-0157055 describe
a copolymer of acryloyldimethyltaurate and dimethylacrylamide in a
molar ratio of 1:4 to 4:1 as a fluid loss additive for
salt-containing (about 10% by weight) cement slurries and the use
of acryloyldimethyltaurate and acrylic acid in a molar ratio of 1:4
to 4:1 for the same purpose.
[0015] Polymers based on acryloyldimethyltaurate or salts thereof
are already known. No solution satisfactory for application
purposes for a temperature range between 30.degree. C. (86.degree.
F.) and 200.degree. C. (392.degree. F.) on the basis of the
monomers disclosed in U.S. Pat. No. 4,015,991 has been described to
date.
[0016] Polymers based on acryloyldimethyltaurate, acrylic acid and
acrylamide are likewise known:
[0017] EP-0244981 discloses polymers based on
acryloyldimethyltaurate, acrylic acid and acrylamide as a
soil-repellent sealing formulation. These polymers are prepared by
the free-radical polymerization of the monomers in an aqueous
medium. Polymers prepared according to examples 1-8 in EP-0244981,
because of their polymer architecture (comparative examples 2, 3
and 4), demonstrably do not bring about any reduction in water loss
when they are used as additive in cement slurries.
[0018] Polymers based on sulfonates and acrylamide, according to
U.S. Pat. No. 4,800,071, are employed as filtration aids in order
to remove sparingly soluble calcium salts from aqueous phosphoric
acid solutions. No use of these polymers as water loss reducers in
cement slurries for cementing deep wells has been disclosed.
[0019] U.S. Pat. No. 4,342,653 discloses polymers based on
acryloyldimethyltaurate and acrylamide.
[0020] These polymers are used as precipitation aids for aqueous
dispersions. The precipitation aids described should have between 1
and 35 mol % of repeat units of acryloyldimethyltaurate, and a
Brookfield viscosity of at least 210.sup.-3 Pas. The example
adduced in U.S. Pat. No. 4,342,653 features an acrylamide content
of 94 mol %. Such a high molar acrylamide content does not lead to
any reduction in water loss in cement slurries.
[0021] JP-11310751 describes polymers based on 10-90 mol % of
acryloyldimethyltaurate, 0-90 mol % of acrylamide and 0-30 mol % of
further copolymerizable monomers suitable for paper coatings,
adhesives and emulsion-based adhesives. These polymers are prepared
by the free-radical polymerization of the monomers in an aqueous
medium. Polymers prepared by the process in JP-11310751, because of
their polymer architecture, do not bring about any reduction in
water loss when they are used as additive in cement slurries.
[0022] JP-63060240 discloses polymers based on
acryloyldimethyltaurate, acrylamides and sodium acrylate, which are
used as precipitants in gold suspensions or gels for gold
separation. The polymer specified in the example contains 13.3 mol
% of AMPS, 13.3 mol % of sodium acrylate and 73.4 mol % of
acrylamide, and was prepared with the aid of an aqueous
free-radical polymerization. However, the disadvantage of these
polymers is an unwanted influence on the cement properties
(reduction in hardened cement strength) and the delaying effect on
the solidification of the cement. As an additive in cement
slurries, the polymer also does not exhibit any effects which
contribute to reduction in water loss in cement slurries.
[0023] Additives on the market which are used as water loss
reducers in cement slurries for cementing deep wells are
acryloyldimethyltaurate and copolymers thereof (e.g.
HOSTAMER.RTM.4707 from Clariant). However, these in turn have the
disadvantage that they lead to an increase in water loss below a
temperature of 180.degree. C. (356.degree. F.).
[0024] The multitude of polymers developed for reduction of water
release makes it clear that it is always problematic to formulate a
cement slurry which is optimal for application purposes for a
temperature range between 30.degree. C. (86.degree. F.) and
200.degree. C. (392.degree. F.). A significant influence on the
suitability thereof is exerted by the temperature of the wellbore
section which is being prepared for cementing. The polymers
optimized for different temperatures constitute major logistical
problems because a certain stock of extra water loss-reducing
polymers always has to be kept at sites all over the world.
[0025] It was therefore an object of the present invention to
provide substances which can help to achieve improved control of
liquid loss in the cement slurries for cementing wellbores at
temperatures between 80.degree. F. and 300.degree. F.
[0026] It has now been found that, surprisingly, the performance
properties required can be achieved through the copolymerization of
acryl-, methacryl- or ethacrylamidoalkylsulfonic acid or salts
thereof and with carboxyalkyl acrylate, methacrylate or ethacrylate
or oligomers of these carboxyl compounds, and with acrylamides or
alkylacrylamides, when the polymerization process is altered and
the subsequent hydrolysis is dispensed with, and hence a novel
polymer which has not been described to date is prepared. This
polymer also does not have any set-delaying properties below
50.degree. C.
[0027] The present invention provides water-soluble or
water-swellable polymers having a k value of 100 to 300, measured
in 0.5% by weight solution in distilled water, containing
[0028] a) 25-35 mol % of one or more recurrent structural units of
the formula (1)
##STR00004##
in which [0029] R.sup.1, R.sup.2 are hydrogen, methyl or ethyl,
[0030] A is linear or branched C.sub.1-C.sub.12-alkylene, and
[0031] Q.sup.+ is H.sup.+, NH.sub.4.sup.+, Li.sup.+, Na.sup.+,
K.sup.+, 1/2 Ca.sup.++, 1/2 Mg.sup.++, 1/2 Zn.sup.++, 1/3
Al.sup.+++, organic ammonium ions of the formula
[HNR.sup.5R.sup.6R.sup.7].sup.+ where R.sup.5, R.sup.6 and R.sup.7
may each independently be hydrogen, a linear or branched alkyl
group having 1 to 22 carbon atoms, a linear or branched, mono- or
polyunsaturated alkenyl group having 2 to 22 carbon atoms, a
C.sub.6-C.sub.22-alkylamidopropyl group, a linear monohydroxyalkyl
group having 2 to 10 carbon atoms or a linear or branched
dihydroxyalkyl group having 3 to 10 carbon atoms, and where at
least one of the R.sup.5, R.sup.6 and R.sup.7 radicals is not
hydrogen, or mixtures of these ions,
[0032] b) 3 to 8 mol % of one or more recurrent structural units of
the formula (2)
##STR00005##
in which [0033] R.sup.1 is hydrogen, methyl or ethyl, [0034]
X.sup.+ is H.sup.+, NH.sub.4.sup.+, Li.sup.+, Na.sup.+, K.sup.+,
1/2 Ca.sup.++, 1/2 Mg.sup.++, 1/2 Zn.sup.++, 1/3 Al.sup.+++,
organic ammonium ions of the formula
[HNR.sup.5R.sup.6R.sup.7].sup.+ where R.sup.5, R.sup.6 and R7 may
each independently be hydrogen, a linear or branched alkyl group
having 1 to 22 carbon atoms, a linear or branched, mono- or
polyunsaturated alkenyl group having 2 to 22 carbon atoms, a
C.sub.6-C.sub.22-alkylamidopropyl group, a linear monohydroxyalkyl
group having 2 to 10 carbon atoms or a linear or branched
dihydroxyalkyl group having 3 to 10 carbon atoms, and where at
least one of the R.sup.5, R.sup.6 and R.sup.7 radicals is not
hydrogen, or mixtures of these ions, [0035] B is a chemical bond,
or a linear or branched alkylene group having 1 to 6 carbon atoms,
and [0036] n is an integer from 0 to 5, and
[0037] c) 57 to 72 mol % of one or more recurrent structural units
of the formula (3)
##STR00006##
in which [0038] R.sup.1 is hydrogen, methyl or ethyl, and [0039]
R.sup.3 and R.sup.4 are each independently hydrogen, methyl, ethyl,
n-propyl, isopropyl or butyl.
[0040] The invention further provides for the use of the polymers
of the invention as water loss reducers for cement formulations.
Preferably, 0.05% to 5% by weight of the polymers, based on the
weight of the cement formulation, is used in cement
formulations.
[0041] In a polymer of the invention, it is possible in each case
for different structural units of the formula (1) and/or of the
formula (2) and/or of the formula (3) to be present. A polymer of
the invention may, for example, contain several structural units of
the formula (1) which differ from one another by different
counterions Q.sup.+. A polymer of the invention may, for example,
also contain several structural units of the formula (2) which
differ from one another by different counterions X.sup.+. A polymer
of the invention may, for example, also contain several structural
units of the formula (3) which differ by different R.sup.1, R.sup.3
and R.sup.4 radicals. The R.sup.1 radicals in the structural units
of the formulae (1), (2) and (3) may be identical or different in
all the structural units.
[0042] The weight-average molecular weights of these polymers are
preferably 300 000 to 5 000 000, more preferably 500 000 to 4 000
000, especially 600 000 to 2 500 000 g/mol. The weight-average
molecular weights can be determined with the aid of gel permeation
chromatography (GPC). The procedure for determining the
weight-average molecular weight with the aid of GPC is described in
detail in "Makromolekulare Chemie: Eine Einfuhrung" [Macromolecular
Chemistry: An Introduction] by Bernd Tieke, Wiley-VCH, 2nd fully
revised and extended edition (Sep. 9, 2005) ISBN-10: 3527313796 in
chapter 3. The polymers were analyzed against a
polystyrenesulfonate standard.
[0043] Indicators used for the molecular weight are the relative
viscosity and the k value. To determine the k value, the copolymer
is dissolved in distilled water in a concentration of 0.5% by
weight and the outflow time at 20.degree. C. is determined by means
of an Ubbelohde viscometer. This value gives the absolute viscosity
of the solution (.eta..sub.c). The absolute viscosity of the
solvent is (.eta..sub.0). The ratio of the two absolute viscosities
gives the relative viscosity:
Z = n c n 0 ##EQU00001##
[0044] The relative viscosity Z and the concentration C can be used
to determine the k value by means of the following equation:
Lg z = ( 75 * k 2 1 + 1.5 kc + k ) * c ##EQU00002##
[0045] The k value of the polymers of the invention is from 100 to
300, preferably from 150 to 270 and especially preferably from 180
to 250.
[0046] In the structural units of the formula (1), R.sup.1 is
preferably hydrogen or methyl and more preferably hydrogen.
[0047] In the structural units of the formula (1), A is preferably
a structural unit of the formula
--C(CH.sub.3).sub.2--CH.sub.2--.
[0048] The structural units of the formula (1) are preferably
derived from monomers from the group consisting of
acryloyldimethyltaurate, acryloyl-1,1-dimethyl-2-methyltaurate,
acryloyltaurate, acryloyl-N-methyltaurate, preferably
acryloyldimethyltaurate.
[0049] Preferably, the neutralization level of the structural units
of the formula (1) is from 50.0 to 100 mol %, more preferably from
80.0 to 100 mol %, especially preferably from 90.0 to 100 mol % and
exceptionally preferably from 95.0 to 100 mol %.
[0050] In the structural units of the formula (1), Q is partly H+
if neutralization is incomplete. In the case of partial or complete
neutralization, Q+ is preferably selected from NH.sub.4.sup.+,
Ca.sup.2+ and Na.sup.+ and mixtures of these ions. More preferably,
the counterion Q other than H.sup.+ is NH.sub.4.sup.+.
[0051] In the structural units of the formula (2), R.sup.1 is
preferably hydrogen or methyl and more preferably hydrogen.
[0052] In the structural units of the formulae (2), B is preferably
a chemical bond or a structural unit of the formula
--CH.sub.2--CH.sub.2--.
[0053] In the structural units of the formula (2), n is preferably
0 to 5 and more preferably 0 to 3 and especially preferably 0 or
1.
[0054] Preferably, the proportion of structural units of the
formula (2) in which n is 0 within component b) of the polymers of
the invention is at least 70.0 mol %, more preferably at least 80.0
mol %, especially preferably at least 90.0 mol %, exceptionally
preferably at least 95.0 mol %.
[0055] More preferably, in the structural units of the formula (2),
B is a chemical bond or the --CH.sub.2CH.sub.2-- group.
[0056] In a further preferred embodiment, in the structural units
of the formula (2), B is a chemical bond or the
--CH.sub.2CH.sub.2-- group and n is an integer from 1 to 5, and
preferably from 1 to 3 and more preferably 1.
[0057] In the structural units of the formula (2), X is partly H+
if neutralization is incomplete. In the case of partial or complete
neutralization, X is preferably selected from NH.sub.4.sup.+,
Ca.sup.2+ and Na.sup.+ and mixtures of these ions. More preferably,
the counterion X that is not H.sup.+ is NH.sub.4.sup.+
[0058] In a further particularly preferred embodiment of the
invention, X.sup.+ is H.sup.+.
[0059] In a further particularly preferred embodiment of the
invention, the polymers of the invention contain several different
structural units of the formula (2), where the counterions X.sup.+
in some structural units of the formula (2) are defined as H.sup.+
and the counterions X.sup.+ in the other structural units of the
formula (2) are defined differently than H.sup.+, and preferably as
NH.sub.4.sup.+.
[0060] In a further particularly preferred embodiment of the
invention, the polymers of the invention contain several different
structural units of the formula (2) which differ in terms of
R.sup.1, b and/or n.
[0061] These structural units are preferably derived from monomers
from the group consisting of methacrylic acid, acrylic acid,
carboxyethyl acrylate and higher oligomers of the formula (2) in
which n is an integer of 2 or more.
[0062] Especially preferably, the structural units are derived from
methacrylic acid, acrylic acid and carboxyethyl acrylate.
Particular preference is given to methacrylic acid and acrylic
acid.
[0063] The structural units of the formula (3) are preferably
derived from monomers from the group consisting of acrylamide,
N-methylacrylamide, N-ethylacrylamide, N,N-diethylmethacrylamide,
N,N-diethylacrylamide, N,N-dimethylmethacrylamide,
N,N-dimethylacrylamide, N-isopropylacrylamide,
N-tert-butylacrylamide and N-butylacrylamide, preferably
acrylamide, methacrylamide, N,N-diethylacrylamide,
N,N-dimethylacrylamide, isopropylacrylamide, more preferably
acrylamide, methacrylamide, N,N-dimethylacrylamide, especially
preferably acrylamide.
[0064] In a further embodiment of the invention, the polymers of
the invention preferably contain
[0065] a) 27.5 to 32.5 mol % of structural units of the formula
(1),
[0066] b) 4.5 to 7.5 mol % of structural units of the formula (2),
and
[0067] c) 60 to 68 mol % of structural units of the formula
(3).
[0068] In a further preferred embodiment of the invention, the
structural units of the formula (1) are derived from
acryloyldimethyltaurate, those of the formula (2) are derived from
acrylic acid and those of the formula (3) are derived from
acrylamide.
[0069] Particularly preferred polymers of the invention contain
structural units of
[0070] a) 25 to 35 mol % of acryloyldimethyltaurate, and
[0071] b) 3 to 8 mol % of acrylic acid, and
[0072] c) 57 to 72 mol % of acrylamide.
[0073] A further embodiment of particularly preferred polymers of
the invention contains structural units of
[0074] a) 27.5 to 32.5 mol % of acryloyldimethyltaurate, and
[0075] b) 4.5 to 7.5 mol % of acrylic acid, and
[0076] c) 60 to 68 mol % of acrylamide.
[0077] In a further preferred embodiment of the invention, the
polymers of the invention do not contain any cationic structural
units.
[0078] The distribution of the different structural units in the
polymers of the invention may be random, blockwise or in
alternating or gradient form. The polymers of the invention are
generally prepared by free-radical polymerization.
[0079] Free-radical polymerizations are common knowledge to those
skilled in the art and are described in detail in standard
literature works, for example in "Makromolekulare Chemie: Eine
Einfuhrung" by Bernd Tieke, Wiley-VCH, 2nd fully revised and
extended edition (Sept. 9, 2005) ISBN-10: 3527313796.
[0080] The polymers of the invention are preferably prepared by
means of free-radical precipitation polymerization in a polar
solvent or solvent mixture. This involves dissolving or dispersing
the corresponding monomers, for example, in the polar solvent or
solvent mixture and initiating the polymerization in a manner known
per se, for example by adding a free radical-forming compound. It
is possible here, for example, for the initially charged monomers
to be polymerized "directly". Alternatively, they may also be
neutralized prior to the polymerization, for example by reacting
acidic groups in monomers used with bases prior to the
polymerization, forming the counterions Q.sup.+ of the structural
units of formula (1) or X.sup.+ of the structural units of formula
(2). Instead of the neutralization of the monomers prior to the
polymerization, however, it is also possible to neutralize the
polymers with the bases on completion of polymerization.
[0081] The present invention therefore further provides a process
for preparing the polymers of the invention, wherein monomers from
which the structural units of components a) to c) derive are
free-radically polymerized in a polar solvent or solvent mixtures
comprising such solvents, and the monomers are optionally
neutralized prior to the polymerization, or the polymer is
neutralized after the polymerization, with ammonia or organic
amines or an Li.sup.+--, Na.sup.+--, K.sup.+--, Ca.sup.++--,
Mg.sup.++--, Zn.sup.++-- or Al.sup.+++-- containing base,
preferably with the corresponding hydroxides or carbonates and more
preferably with hydroxides.
[0082] Useful polymerization initiators include all free
radical-forming substances; as well as typical diazo compounds and
peroxy compounds, initiation is also possible by means of redox
initiators, a photoinitiator or by means of high-energy radiation
(UV, neutrons, plasma). In contrast to aqueous free-radical
polymerization, there is only a minor dependence of the product on
the type and amount of the initiator system used.
[0083] In a preferred embodiment of the process for preparing the
polymers of the invention, the free-radical precipitation
polymerization is effected in a polar solvent or solvent mixture
which is characterized in that the solvent or solvent mixture has a
boiling point of 60 to 110.degree. C., preferably of 60 to
85.degree. C., more preferably of 70 to 85.degree. C.
[0084] In a further preferred embodiment of the process for
preparing the polymers of the invention, the polar solvent
contains:
[0085] d) water and
[0086] e) one or more further polar solvents, preferably alcohols,
dialkyl ketone and cyclic ethers, more preferably alcohols, dialkyl
ketone and especially preferably alcohols.
[0087] In a further preferred embodiment of the process for
preparing the polymers of the invention, component e) contains one
or more polar solvents selected from the group of methanol,
ethanol, 1-propanol, 2-propanol, 2-methyl-2-propanol, 2-butanol,
dimethyl ketone, diethyl ketone, tetrahydropyran, tetrahydrofuran,
2-methyltetrahydrofuran, 1,3-dioxane, 1,4-dioxane, preferably
ethanol, 1-propanol, 2-propanol, 2-methylpropan-2-ol, 2-butanol,
dimethyl ketone, tetrahydrofuran, 2-methyltetrahydrofuran,
1,3-dioxane, more preferably 2-propanol, 2-methylpropan-2-ol,
dimethyl ketone, tetrahydrofuran, 2-methyltetrahydrofuran,
1,3-dioxane, especially preferably 2-methylpropan-2-ol, dimethyl
ketone and exceptionally preferably 2-methylpropan-2-ol.
[0088] In the process for preparing the polymers of the invention,
it is possible for various polar solvents of component e) to be
present. One polar solvent of the invention in component e) may,
for example, comprise 2-methylpropan-2-ol. A further solvent of the
invention in component e) may, for example, comprise a mixture of
2-methylpropan-2-ol and dimethyl ketone. A further solvent of the
invention in component e) may, for example, comprise a mixture of
2-methylpropan-2-ol and tetrahydrofuran.
[0089] In a particular embodiment of the process for preparing a
polymer of the invention, the polar solvent mixture contains 0.5%
to 20% by weight, preferably 0.5% to 10% by weight and more
preferably 1% to 8% by weight of water and exceptionally preferably
2% to 5% by weight of water.
[0090] In a further particular embodiment of the process for
preparing a polymer of the invention, the polar solvent mixture
contains 5% to 99.5% by weight, preferably 10% to 99.5% by weight
and more preferably 30% to 99.5% by weight of
2-methylpropan-2-ol.
[0091] In a further particular embodiment of the process for
preparing a polymer of the invention, the polar solvent mixture
contains 0.5% to 20% by weight of water, 7.5% to 92% by weight of
2-methylpropan-2-ol and 7.5% to 92% by weight of dimethyl ketone,
preferably 0.5% to 7.5% by weight of water, 20% to 89.5% by weight
of 2-methylpropan-2-ol and 10% to 79.5% by weight of dimethyl
ketone.
[0092] In an exceptionally preferred process for preparing an
inventive polymer, 27.5 to 32.5 mol % of acryloyldimethyltaurate,
4.5 to 7.5 mol % of acrylic acid and 60 to 68 mol % of acrylamide
are free-radically polymerized in a polar solvent mixture,
preferably a mixture of 1% to 8% by weight of water and 92% to 99%
by weight of 2-methylpropan-2-ol, and the monomers are optionally
neutralized prior to the polymerization, or the polymer is
neutralized after the polymerization, with ammonia, ammonium
carbonate, sodium hydroxide, sodium carbonate, preferably with
ammonia.
[0093] The polymers are obtained as a white voluminous precipitate
in the polar solvent mixture. For isolation, it is possible to use
all the customary evaporation and drying isolation processes. More
particularly, the polar solvent mixture can be removed from the
product by a pressure filtration or distillation. A small residue
of the polar solvent mixture is of no concern, either for safety
reasons or for application reasons.
[0094] The invention further provides a method for cementing deep
wells using a cement slurry containing the polymer of the invention
in a concentration of 0.01% to 5% bwoc (by weight of cement),
preferably 0.05% to 0.9% bwoc. Further components of the cement
slurry are waters of different salinity and cement. In addition, it
is possible to use dispersants, retardants, accelerators,
extenders, foamers, defoamers, weighting agents, density-reducing
additives and tensile strength-increasing fibers or silicate
derivatives as auxiliary additives.
[0095] The invention further provides a method for cementing deep
wells using a cement slurry containing a mixture of the inventive
polymer and starch in a concentration of 0.01% to 5% bwoc (by
weight of cement), preferably 0.05% to 0.9% bwoc. Further
components of the cement slurry are waters of different salinity
and cement. In addition, it is possible to use dispersants,
retardants, accelerators, extenders, foamers, defoamers, weighting
agents, density-reducing additives and tensile strength-increasing
fibers or silicate derivatives as auxiliary additives.
[0096] The term "starch" is understood to mean an organic compound.
Starch is a polysaccharide having the formula
(C.sub.6H.sub.10O.sub.5).sub.n which consists of .alpha.-D-glucose
units joined to one another via glycosidic bonds. Starch may
consist of: [0097] 0% to 100% by weight of amylose, linear chains
having a helical (screw) structure, having only
.alpha.-1,4-glycosidic linkages, and [0098] 0% to 100% by weight of
amylopectin, highly branched structures, having
.alpha.-1,6-glycosidic and .alpha.-1,4-glycosidic linkages.
However, the amylopectin of starch, with about one
.alpha.-1,6-glycosidic bond after about 30 .alpha.-1,4-glycosidic
linkages, is less highly branched than that of glycogen (about 1
.alpha.-1,6-glycosidic bond for every 10 .alpha.-1,4-glycosidic
bonds).
[0099] In this part of the world, starch is usually obtained from
potatoes or cereals, but also from numerous other plants, such as
rice (broken rice from rice dehusking factories) and corn. Another
starch-providing plant of international significance is manioc
(tapioca). In industrial starch production, various technologies
are used according to the raw material.
[0100] In a particular embodiment of the invention, the starch can
be thermally modified in an upstream step. The starch can
physically bind several times its own weight of water, swell up and
gelatinize under the action of heat. When heated with water, the
starch swells at 47-57.degree. C., the layers break up and
gelatinized starch forms at 55-87.degree. C. (potato starch at
62.5.degree. C., wheat starch at 67.5.degree. C.), having different
stiffening capacity according to the starch type. The use of
natural, non-pregelatinized starch has the advantage that, during
the pumping of a cement slurry, this cement slurry is rheologically
stabilized when the temperature increases.
[0101] In a further particular embodiment of the invention, the
starch may be in a chemically modified form. Modified starch,
according to which properties are to be modified, is produced by
various chemical conversion processes. In the case of some modified
starches, several conversion processes are conducted in succession
(e.g. acetylated oxidized starch). Modified starches modified by
chemical conversion processes are understood to mean: [0102]
acid-treated starch by reaction with acids (for example with
hydrochloric acid, phosphoric acid or sulfuric acid) [0103]
alkali-modified starch by reaction with alkalis (for example with
sodium hydroxide solution or potassium hydroxide solution) [0104]
bleached starch by treatment with peroxyacetic acid, hydrogen
peroxide, sodium hypochlorite, sodium chlorite, sulfur dioxide,
sulfites, potassium permanganate or ammonium persulfate [0105]
enzymatically modified starch by treatment with amylases oxidized
starch by oxidation (for example with sodium hypochlorite) [0106]
monostarch phosphate by esterification with phosphorous ester
groups (for example phosphoric acid, sodium phosphate or potassium
phosphate, phosphonic acid or pentasodium triphosphate) [0107]
distarch phosphate by esterification with sodium trimetaphosphate
or phosphorus oxychloride [0108] phosphated distarch phosphate by
combination of the processes for preparing monostarch phosphate and
distarch phosphate [0109] acetylated starch by esterification (for
example with anhydrides) [0110] hydroxypropyl starch by reaction
with propylene oxide [0111] sodium octenylsuccinate starch by
reaction of starch with octenylsuccinic anhydride.
[0112] The most commonly desired improvements are in resistance to
heat, cold and/or pH changes (acids).
[0113] The invention therefore further provides mixtures comprising
the abovementioned starch and/or modifications thereof and the
polymers of the invention. These mixtures preferably contain:
[0114] 25% to 75% by weight of starch and 25% to 75% by weight of
the polymers of the invention.
[0115] In a particular embodiment, the mixtures contain 25% to 75%
by weight of a chemically modified starch and 25% to 75% by weight
of the polymers of the invention.
[0116] In a further particular embodiment, the mixtures contain 25%
to 75% by weight of a thermally modified starch and 25% to 75% by
weight of the polymers of the invention.
[0117] An inventive mixture of starch and the polymers of the
invention can be obtained during the polymerization process after
the actual polymerization and before the drying operation or
isolation operation.
[0118] A further inventive mixture of starch and the polymers of
the invention can be obtained by the mixing of the pulverulent
starch with the pulverulent polymer of the invention.
EXAMPLES
[0119] In polymerization processes A to B described below, typical
preparation processes for the polymers of the invention are
described.
[0120] In the examples, there was variation of the polar solvent
used, with the aid of which the polymers of the invention can be
prepared. With the aid of polymerization methods A1 to A5 and B1 to
B3, further polymers of the invention were prepared by the
variation of the monomers. These polymers and polymerization
processes used for the synthesis thereof are summarized in table
1a) to table 1i).
Polymerization process A1: Polymerization in
2-methylpropan-2-ol/water (3.5%) as polar solvent
[0121] In a 2 liter Quickfit flask with anchor stirrer, reflux
condenser with offgas scrubber, combined thermometer/pH meter and a
gas inlet tube, 772 g of anhydrous 2-methyl-propan-2-ol are admixed
with 28 g of distilled water. The reaction vessel is within a
thermostatted heating bath.
[0122] This reaction vessel is blanketed with nitrogen gas and, in
a gentle nitrogen countercurrent, 113.2 g of
acryloyldimethyltaurate are introduced. The acryloyldimethyltaurate
does not dissolve completely in the 2-methylpropan-2-ol/water
mixture and is partly in the form of a dispersion of solids. The pH
of this mixture is below pH 1. Through the gas inlet tube, gaseous
ammonia is introduced above the liquid phase until the pH of the
dispersion is between 7 and 8. On attainment of the desired pH
range, the mixture is stirred for another 1 hour and the pH is
recorded continuously. The reaction vessel is blanketed with
nitrogen and 79.2 g of acrylamide and 7.6 g of acrylic acid are
introduced. After the acrylamide has been introduced, the pH is
checked again and optionally corrected into the pH range of 7 to 8.
A constant nitrogen stream is passed through the solution for at
least 1 hour. After this inertization time, the residual oxygen is
checked by means of an oxygen electrode. Should the measured value
of residual oxygen in the liquid phase exceed the value of 1 ppm,
another inertization is necessary until this value is attained.
Thereafter, in a gentle nitrogen stream, 2 g of
2,2'-azobis(2,4-dimethylvaleronitrile) are added and the reaction
tank is heated to 40.degree. C. Shortly after attainment of an
internal temperature of 40.degree. C., the introduction of nitrogen
gas is ended and commencement of the polymerization reaction is
observed, which can be identified by a temperature increase of
10-35.degree. C. About 5-15 minutes after onset of the
polymerization reaction, the temperature maximum has been exceeded
and the temperature in the reaction vessel is increased by means of
the heating bath up to the boiling point of the
2-methylpropan-2-ol/water mixture. Under gentle reflux, the now
viscous mixture is stirred for a further two hours. The reaction
product, present in the form of a viscous suspension of polymer in
the 2-methylpropan-2-ol/water mixture, is removed by filtration and
subsequent drying in a vacuum drying cabinet.
[0123] Yield: 215.4 g of polymer 1
[0124] Dry content (IR drier, 15 minutes at 120.degree. C.):
94%
[0125] K value (0.5% solution in distilled water): 212
[0126] pH (0.5% solution in distilled water): 4.76
Polymerization process A2: Polymerization in
2-methylpropan-2-ol/water (2%) In a 2 liter Quickfit flask with
anchor stirrer, reflux condenser with offgas scrubber, combined
thermometer/pH meter and a gas inlet tube, 784 g of anhydrous
2-methylpropan-2-ol are admixed with 16 g of distilled water. The
reaction vessel is within a thermostatted heating bath. The further
steps of polymerization process A2 are conducted analogously to
polymerization process A1.
[0127] With the aid of polymerization method A2, further polymers
of the invention were prepared by varying the monomers. These
polymers are summarized in table 1.
[0128] Polymerization process A3: Polymerization in
2-methylpropan-2-ol/water (4.5%)
[0129] In a 2 liter Quickfit flask with anchor stirrer, reflux
condenser with offgas scrubber, combined thermometer/pH meter and a
gas inlet tube, 764 g of anhydrous 2-methylpropan-2-ol are admixed
with 36 g of distilled water. The reaction vessel is within a
thermostatted heating bath. The further steps of polymerization
process A3 are conducted analogously to polymerization process
A1.
Polymerization process A4: Polymerization in
2-methylpropan-2-ol/water (1.5%)
[0130] In a 2 liter Quickfit flask with anchor stirrer, reflux
condenser with offgas scrubber, combined thermometer/pH meter and a
gas inlet tube, 788 g of anhydrous 2-methylpropan-2-ol are admixed
with 12 g of distilled water. The reaction vessel is within a
thermostatted heating bath. The further steps of polymerization
process A4 are conducted analogously to polymerization process
A1.
Polymerization process A5: Polymerization in
2-methylpropan-2-ol/water (7.5%)
[0131] In a 2 liter Quickfit flask with anchor stirrer, reflux
condenser with offgas scrubber, combined thermometer/pH meter and a
gas inlet tube, 748 g of anhydrous 2-methylpropan-2-ol are admixed
with 52 g of distilled water. The reaction vessel is within a
thermostatted heating bath. The further steps of polymerization
process A5 are conducted analogously to polymerization process
A1.
Polymerization process B1: Polymerization in 2-methylpropan-2-ol,
dimethyl ketone and water as polar solvent (50:50, 3.4% water)
[0132] In a 2 liter Quickfit flask with anchor stirrer, reflux
condenser with offgas scrubber, combined thermometer/pH meter and a
gas inlet tube, 384 g of anhydrous 2-methylpropan-2-ol and 384 g of
dimethyl ketone are admixed with 26.4 g of distilled water. The
reaction vessel is within a thermostatted heating bath.
[0133] This reaction vessel is blanketed with nitrogen gas and, in
a gentle nitrogen countercurrent, 130 g of acryloyldimethyltaurate
are introduced. The acryloyldimethyltaurate does not dissolve
completely in the 2-methylpropan-2-ol/dimethyl ketone/water mixture
and is partly in the form of a dispersion of solids. The pH of this
mixture is below pH 1. Through the gas inlet tube, gaseous ammonia
is introduced above the liquid phase until the pH of the dispersion
is between 7 and 8. On attainment of the desired pH range, the
mixture is stirred for another 1 hour and the pH is recorded
continuously. The reaction vessel is blanketed with nitrogen and 60
g of acrylamide and 10 g of acrylic acid are introduced. After the
acrylamide has been introduced, the pH is checked again and
optionally corrected into the pH range of 7 to 8. A constant
nitrogen stream is passed through the solution for at least 1 hour.
After this inertization time, the residual oxygen is checked by
means of an oxygen electrode. Should the measured value of residual
oxygen in the liquid phase exceed the value of 1 ppm, another
inertization is necessary until this value is attained. Thereafter,
in a gentle nitrogen stream, 2.05 g of
2,2'-azobis(2,4-dimethylvaleronitrile) are added and the reaction
tank is heated to 40.degree. C. Shortly after attainment of an
internal temperature of 40.degree. C., the introduction of nitrogen
gas is ended and commencement of the polymerization reaction is
observed, which can be identified by a temperature increase of 10
to 35.degree. C. About 5-15 minutes after onset of the
polymerization reaction, the temperature maximum has been exceeded
and the temperature in the reaction vessel is increased by means of
the heating bath up to the boiling point of the
2-methylpropan-2-ol/water mixture. Under gentle reflux, the now
viscous mixture is stirred for a further two hours. The reaction
product, present in the form of a viscous suspension of polymer in
the 2-methylpropan-2-ol/water mixture, is removed by filtration and
subsequent drying in a vacuum drying cabinet.
Polymerization process B2: Polymerization in 2-methylpropan-2-ol,
dimethyl ketone and water as polar solvent (75:25, 3.0% water)
[0134] In a 2 liter Quickfit flask with anchor stirrer, reflux
condenser with offgas scrubber, combined thermometer/pH meter and a
gas inlet tube, 582 g of anhydrous 2-methylpropan-2-ol and 194 g of
dimethyl ketone are admixed with 24 g of distilled water. The
reaction vessel is within a thermostatted heating bath. The further
steps of polymerization process B2 are conducted analogously to
polymerization process B1.
Polymerization process B3: Polymerization in 2-methylpropan-2-ol,
dimethyl ketone and water as polar solvent (25:75, 5.0% water)
[0135] In a 2 liter Quickfit flask with anchor stirrer, reflux
condenser with offgas scrubber, combined thermometer/pH meter and a
gas inlet tube, 194 g of anhydrous 2-methylpropan-2-ol and 582 g of
dimethyl ketone are admixed with 24 g of distilled water. The
reaction vessel is within a thermostatted heating bath. The further
steps of the polymerization process are conducted analogously to
polymerization process B1.
TABLE-US-00001 TABLE 1a Examples of polymers of the invention
prepared by polymerization processes A1 to A5 and B1 to B3 ACDMT
Acrylic acid Acrylamide V-65 .RTM. mol mol mol % by k Polymer
Process g % g % g % g wt. value 2 A1 110.0 29.6 10.00 7.7 80.0 62.7
2.00 1.0 215 4 A1 113.2 30.9 7.60 6.0 79.2 63.1 2.00 1.0 210 6 A1
98.0 32.0 6.40 6.0 65.0 61.9 1.90 1.1 208 7 A1 119.0 32.5 5.70 4.5
79.2 63.0 2.25 1.1 200 8 A1 104.5 28.5 9.60 7.5 80.4 64.0 2.25 1.2
204 12 A2 110.0 29.6 10.00 7.7 80.0 62.7 2.25 1.1 192 13 A2 113.2
30.9 7.60 6.0 79.2 63.1 2.20 1.1 188 14 A2 119.0 32.5 5.70 4.5 79.2
63.0 2.20 1.1 179 16 A3 113.2 30.9 7.60 6.0 79.2 63.1 2.20 1.1 216
18 A3 110.0 29.6 10.00 7.7 80.0 62.7 2.25 1.1 222 20 A4 90.0 25.1
6.20 5.0 86.0 69.9 2.18 1.2 176
TABLE-US-00002 TABLE 1b Examples of polymers of the invention
prepared by polymerization processes A1 to A5 and B1 to B3 ACDMT
Acrylic acid Acrylamide V-65 .RTM. mol mol mol % by k Polymer
Process g % g % g % g wt. value 25 B1 109.5 29.5 9.70 7.5 80.3 63.0
2.30 1.2 203 26 B1 100.0 28.5 6.10 5.0 80.0 66.5 2.10 1.1 211 28 B1
113.2 31.0 7.60 6.0 79.0 63.0 2.20 1.1 213 31 B2 99.5 34.5 8.00 8.0
56.8 57.5 1.80 1.1 219 33 B2 110.0 34.3 3.40 3.0 69.0 62.7 2.00 1.1
227 34 B2 119.0 32.5 5.70 4.5 79.2 63.0 2.25 1.1 228 35 B2 110.0
29.6 10.00 7.7 80.0 62.7 2.25 1.1 221 36 B2 113.2 30.9 7.60 6.0
79.2 63.1 2.25 1.1 227 38 B3 113.2 30.9 7.60 6.0 79.2 63.1 2.20 1.1
216 40 B3 110.0 29.6 10.00 7.7 80.0 62.7 2.25 1.1 218
TABLE-US-00003 TABLE 1c Polymers of the invention by polymerization
process A1 Methacrylic ACDMT acid Acrylamide V-65 .RTM. k Polymer
Process mol % mol % mol % g value 42 A1 30 7 63 2.00 208 44 A1 31 6
63 2.00 219
TABLE-US-00004 TABLE 1d Polymers of the invention by polymerization
process A1 Methacrylic Dimethyl- ACDMT acid acrylamide V-65 .RTM. k
Polymer Process mol % mol % mol % g value 47 A1 30 7 63 2.0 201 49
A1 31 6 63 2.0 198
TABLE-US-00005 TABLE 1e Polymers of the invention by polymerization
process A1 ACDMT CEA Acrylamide V-65 .RTM. k Polymer Process mol %
mol % mol % g value 52 A1 30 7 63 2.0 217 54 A1 31 6 63 2.0 209
TABLE-US-00006 TABLE 1f Polymers of the invention by polymerization
process A1 Dimethyl- ACDMT CEA acrylamide V-65 .RTM. k Polymer
Process mol % mol % mol % g value 57 A1 30 7 63 2.0 218 59 A1 31 6
63 2.0 207
TABLE-US-00007 TABLE 1g Polymers of the invention by polymerization
process A1 CEA oligomer Acrylamide Polymer Process ACDMT mol % mol
% mol % V-65 .RTM. g k value 62 A1 30 7 63 2.0 214 64 A1 31 6 63
2.0 205
TABLE-US-00008 TABLE 1h Polymers of the invention by polymerization
process A1 CEA Dimethyl- ACDMT oligomer acrylamide V-65 .RTM. k
Polymer Process mol % mol % mol % g value 67 A1 30 7 63 2.0 208 69
A1 31 6 63 2.0 218
[0136] ACDMT=acryloyldimethyltaurate
[0137] AA=acrylic acid
[0138] AM=acrylamide
[0139] CEA=carboxyethyl acrylate
[0140] CEA oligomer=carboxyethyl acrylate oligomer mixture with n
=0 to 5
[0141] V-65=2,2'-azobis(2,4-dimethylvaleronitrile)/V-65 is a
registered trademark of Wako Pure Chemicals Industries, Ltd
Comparative Example 1 (not in accordance with the invention,
prepared according to EP-1045869, copolymer prepared in
precipitation polymerization, 44.5 mol % of acryloyldimethyltaurate
and 55.5 mol % of acrylamide)
[0142] In a 3 liter Quickfit flask with anchor stirrer, reflux
condenser with offgas scrubber, combined thermometer/pH meter and a
gas inlet tube, 1700 g of anhydrous 2-methylpropan-2-ol are admixed
with 50 mL of distilled water. The reaction vessel is within a
thermostatted heating bath.
[0143] This reaction vessel is blanketed with nitrogen gas and, in
a gentle nitrogen countercurrent, 245 g of acryloyldimethyltaurate
are introduced. The acryloyldimethyltaurate does not dissolve
completely in the 2-methylpropan-2-ol/water mixture and is partly
in the form of a dispersion of solids. The pH of this mixture is
below pH 1. Through the gas inlet tube, gaseous ammonia is
introduced above the liquid phase until the pH of the dispersion is
between 7 and 8. On attainment of the desired pH range, the mixture
is stirred for another 1 hour and the pH is recorded continuously.
The reaction vessel is blanketed with nitrogen and 105 g of
acrylamide are introduced. After the acrylamide has been
introduced, the pH is checked again and optionally corrected into
the pH range of 7 to 8. A constant nitrogen stream is passed
through the solution for at least 1 hour. After this inertization
time, the residual oxygen is checked by means of an oxygen
electrode. Should the measured value of residual oxygen in the
liquid phase exceed the value of 1 ppm, another inertization is
necessary until this value is attained. Thereafter, in a gentle
nitrogen stream, 2 g of AIBN are added and the reaction tank is
heated to 60.degree. C. Shortly after attainment of an internal
temperature of 60.degree. C., the introduction of nitrogen gas is
ended and commencement of the polymerization reaction is observed,
which can be identified by a temperature increase of 10-15.degree.
C. About 5-15 minutes after onset of the polymerization reaction,
the temperature maximum has been exceeded and the temperature in
the reaction vessel is increased by means of the heating bath up to
the boiling point of the 2-methylpropan-2-ol/water mixture. Under
gentle reflux, the now viscous mixture is stirred for a further two
hours. The reaction product, present in the form of a viscous
suspension of polymer in the 2-methylpropan-2-ol/water mixture, is
removed by filtration and subsequent drying in a vacuum drying
cabinet.
[0144] Yield: 365 g
[0145] Dry content (IR drier, 15 minutes at 120.degree. C.):
96%
[0146] K value (0.5% solution in distilled water): 212
Comparative Example 2 (not in accordance with the invention,
prepared according to EP-0244981, copolymer prepared in an aqueous
gel polymerization, 18.6 mol % of acryloyldimethyltaurate, 10 mol %
of acrylic acid and 71.3 mol % of acrylamide)
[0147] In EP-0244981, reference is made in the examples to a gel
polymerization in a conventional manner. No detailed preparation
process for the polymers in EP-0244981 is described.
[0148] For comparative example 2, a 1 liter Quickfit flask with
anchor stirrer, reflux condenser with offgas scrubber, combined
thermometer/pH meter and a gas inlet tube was initially charged
with 390 g of distilled water, 40 g of acryloyldimethyltaurate, 7.5
g of acrylic acid and 52.5 g of acrylamide. Nitrogen gas is passed
through the reaction solution for 1 hour. Thereafter, 2 g of
ammonium peroxodisulfate dissolved in 10 g of distilled water are
added as initiator. This mixture is heated to 40.degree. C. until a
polymerization reaction occurs after 10-15 minutes. After passing
through the temperature maximum, the internal temperature is
adjusted to 60.degree. C. by means of the thermostat. A clear gel
of high viscosity forms. The gel is comminuted mechanically and
dried in a vacuum drying cabinet.
Comparative Example 3 (not in accordance with the invention,
prepared according to EP-0244981, copolymer prepared in an aqueous
gel polymerization, 34 mol % of acryloyldimethyltaurate, 11.4 mol %
of acrylic acid and 54.6 mol % of acrylamide).
[0149] For comparative example 3, a 1 liter Quickfit flask with
anchor stirrer, reflux condenser with offgas scrubber, combined
thermometer/pH meter and a gas inlet tube was initially charged
with 390 g of distilled water, 60 g of acryloyldimethyltaurate, 7 g
of acrylic acid and 11.4 g of acrylamide. Nitrogen gas is passed
through the reaction solution for 1 hour. Thereafter, 2 g of
ammonium peroxodisulfate dissolved in 10 g of distilled water are
added as initiator. This mixture is heated to 40.degree. C. until a
polymerization reaction occurs after 10-15 minutes. After passing
through the temperature maximum, the internal temperature is
adjusted to 60.degree. C. by means of the thermostat. A clear gel
of high viscosity forms. The gel is comminuted mechanically and
dried in a vacuum drying cabinet.
Comparative Example 4 (not in accordance with the invention,
prepared according to EP-0244981, copolymer prepared in an aqueous
gel polymerization, 10.3 mol % of acryloyldimethyltaurate, 5.9 mol
% of acrylic acid and 84.9 mol % of acrylamide). Comparative
example 4 was prepared analogously to comparative example 2.
[0150] For comparative example 4, a 1 liter Quickfit flask with
anchor stirrer, reflux condenser with offgas scrubber, combined
thermometer/pH meter and a gas inlet tube was initially charged
with 390 g of distilled water, 25 g of acryloyldimethyltaurate, 5 g
of acrylic acid and 70 g of acrylamide. Nitrogen gas is passed
through the reaction solution for 1 hour. Thereafter, 2 g of
ammonium peroxodisulfate dissolved in 10 g of distilled water are
added as initiator. This mixture is heated to 40.degree. C. until a
polymerization reaction occurs after 10-15 minutes. After passing
through the temperature maximum, the internal temperature is
adjusted to 60.degree. C. by means of the thermostat. A clear gel
of high viscosity forms. The gel is comminuted mechanically and
dried in a vacuum drying cabinet.
Comparative Example 5 (not in accordance with the invention,
prepared according to U.S. Pat. No. 4,015,991, copolymer prepared
in an aqueous gel polymerization, 10.3 mol % of
acryloyldimethyltaurate, 5.9 mol % of acrylic acid and 84.9 mol %
of acrylamide).
[0151] A 3 liter Quickfit flask with anchor stirrer, reflux
condenser with offgas scrubber, combined thermometer/pH meter and a
gas inlet tube is initially charged with 328 g of distilled water
and 116.4 g of acryloyldimethyltaurate. The acryloyldimethyltaurate
is neutralized by adding 45 g of a 50% sodium hydroxide (NaOH)
solution. After the neutralization reaction, a clear solution
having a pH between 7 and 8 is obtained. 14.7 g of acrylamide are
dissolved gradually in the solution thus neutralized. Nitrogen gas
is passed through the reaction solution for 1 hour. Thereafter,
0.69 g of tert-butyl peroxypivalate and 1.0 mL of an iron ammonium
sulfate solution as redox initiator pair are added. The iron
ammonium sulfate solution is prepared by dissolving 0.098 g of
Fe(NH.sub.4).sub.2(SO.sub.4).sub.2 in 500 g of water. This mixture
is additionally stirred at room temperature until, after 1-2 hours,
a polymerization reaction occurs. The exothermic polymerization
reaction, in the case of adiabatic polymerization, increases the
temperature to 50-60.degree. C. After passing through the
temperature maximum, the internal temperature is adjusted to
60.degree. C. by means of the thermostat. A clear gel of high
viscosity is formed. The gel is comminuted mechanically and dried
on a roller drier.
[0152] Yield: 152 g of comparative polymer 5
[0153] According to the testing in U.S. Pat. No. 4,015,991, this
base polymer should have only poor water-loss reducing action. In
contrast, at low temperatures, 28.degree. C., the partly hydrolyzed
products should have good performance properties. These products
were prepared and tested as in comparative example 6.
Comparative Example 6 (not in accordance with the invention,
prepared according to U.S. Pat. No. 4,015,991) Controlled
hydrolysis of comparative polymer 5
[0154] 45.3 g of comparative polymer 5 are dissolved in 1500 mL of
distilled water while stirring. On completion of dissolution of the
polymer, 1.68 g of potassium hydroxide which have been dissolved in
20 mL of water beforehand are added thereto. This mixture is heated
to 60.degree. C. then stirred at this temperature for one hour. The
reaction product is dried again with the aid of a roller drier. In
this way, 50% hydrolysis is achieved.
Examples: Synergistic Mixtures Comprising Starch and the Polymers
of the Invention.
[0155] For the synergistic mixtures comprising starch and the
polymers of the invention, the following starch types were
used:
[0156] Starch A: corn starch
[0157] Starch B: manioc starch
[0158] Starch C: "cook up modified starch"
[0159] Starch D: hydroxypropyl starch
[0160] Table 2 describes the mixtures made with the starches A to E
and the polymers of the invention.
TABLE-US-00009 TABLE 2a Synergistic mixtures comprising starch and
the polymers of the invention Mixture Starch % by wt. Polymer % by
wt. 1 A 30 (4) 70 2 A 50 (4) 50 3 A 70 (4) 30 4 B 50 (4) 50 5 D 60
(4) 40 6 A 25 (42) 75 7 A 40 (42) 60 8 A 65 (42) 35 9 B 25 (42) 75
10 B 40 (42) 60 11 B 65 (42) 35 12 B 50 (52) 50 13 C 50 (52) 50 14
D 50 (52) 50
TABLE-US-00010 TABLE 2b Synergistic mixtures comprising starch and
the polymers of the invention Mixture Starch % by wt. Polymer % by
wt. 15 D 40 (52) 60 16 D 60 (52) 40 17 A 75 (7) 25 18 D 50 (7) 50
25 A 45 (26) 55 26 E 65 (26) 35 27 A 50 (49) 50 28 A 45 (49) 50 29
A 65 (49) 35 30 B 50 (49) 50 31 C 45 (49) 50 32 D 65 (49) 35 33 A
50 (54) 50 34 B 50 (54) 50 35 D 50 (54) 50
Examples: Test Results
[0161] The testing is effected according to API spec. 10. In an
atmospheric consistometer, the cement slurry is stirred/conditioned
at analysis temperature and then, at the same temperature, the
rheology with the FANN model 35SA viscometer is measured (at high
temperature, conditioning is effected at 93.degree. C. and the
viscosity is measured). At temperatures of >93.degree. C., the
water loss is measured with a stirring fluid loss apparatus
(SFLA).
[0162] Table 3 shows the water loss-reducing properties of selected
abovementioned examples according to API spec. 10 at 35.degree. C.
(95.degree. F.) in a static filtration test in the Baroid HTHP
filter press. It becomes clear that the water loss reduction with
the polymers of the invention can be improved considerably at low
temperatures compared to the comparative examples. Of course, at
these low temperatures, the polymers based on
acryloyldimethyltaurate and acrylamide as claimed in EP-1045869,
reworked in comparative example 1, also reduce water loss. However,
it becomes clear from table 1 that the water loss of comparative
example 1 is nearly twice as high compared to the inventive polymer
4. The gel polymers described in EP-0244981, reworked in
comparative examples 2 to 3, show a high water loss even at very
low temperatures and are unsuitable for use. For this reason,
comparative examples 2 to 3 were not considered in the measurements
which follow. The two comparative examples from U.S. Pat. No.
4,015,991, based on partly hydrolyzed
poly(acrylamide-co-acryloyldimethyltaurate), reworked in
comparative examples 5 and 6, in direct comparison with polymer 4,
likewise have nearly twice to three times the water loss. These
polymers too appear unsuitable for use.
[0163] Formulation of the cement slurries:
[0164] 100 g of Dyckerhoff Class G
[0165] 44 g of distilled water
[0166] 0.3-0.5 g of polymer
TABLE-US-00011 TABLE 3 (Use test at 95.degree. F. (35.degree. C.))
Rheology after mixing at 75.degree. F. (24.degree. C.), scale
divisions at X revolutions per minute Polymer Concentration
Revolutions per minute (rpm) API fluid No. % by wt. 600 300 200 100
6 3 loss mL 2 (P) 0.5 95 74 46 33 6 3 60 4 (P) 0.3 108 77 44 30 5
3.5 58 8 (P) 0.3 103 73 39 28 4 3 72 13 (P) 0.3 90 72 38 25 4 3 75
16 (P) 0.3 110 87 53 36 5 3.5 95 18 (P) 0.3 95 73 45 26 4 3 85 20
(P) 0.5 88 67 47 28 4.5 3.5 66 28 (P) 0.3 87 69 39 26 5 3 65 33 (P)
0.3 98 82 59 30 6 3.5 70 36 (P) 0.3 86 63 42 30 5 3.5 68 1 (C) 0.3
94 68 39 26 5 3 115 2 (C) 0.3 290 167 118 67 7.5 4.5 470* 3 (C) 0.3
120 105 77 56 11 5 660* 4 (C) 0.3 275 151 116 59 9 6.5 270* 5 (C)
0.3 168 88 68 38 11 11.5 143* 6 (C) 0.3 225 117 84 43 7 4.5 178*
(P) = inventive polymer (ex.: 30 (P) = inventive polymer 30 from
Table 1a)) (C) = non-inventive comparative example (ex. 5 (C) =
comparative example 5) *values are calculated, since all the water
had been expressed before the test had ended.
[0167] Table 4 shows the water loss-reducing properties of selected
abovementioned examples according to API spec. 10 at 121.1.degree.
C. (250.degree. F.) in a stirred filtration test in the Fann HTHP
filter press (stirring fluid loss apparatus, SFLA). In order to
better show the improved properties of the polymers of the
invention compared to the state of the art of the polymers claimed
in EP1045869 (comparative example 1), the concentration of the
polymers used was varied between 0.25% and 0.5% by weight. It
becomes clear that, with the polymers of the invention at lower
concentrations (0.25% by weight), water loss is reduced by 40%
compared to by weight (80 mL) than with the claimed polymers in EP
1045869 (130 mL).
[0168] Formulation of the cement slurries:
[0169] 100 g of Dyckerhoff Class G Cement
[0170] 35 g of silica flour
[0171] 54.8 g of distilled water
[0172] Polymer in the concentration specified in table 3 or 4
[0173] 0.3 g of dispersant (polynaphthalenesulfonate, PNS)
[0174] 0.5 g of retarder (lignosulfonate)
TABLE-US-00012 TABLE 4 (Use test at 250.degree. F. (121.1.degree.
C.)) Rheology after mixing at 75.degree. F. (24.degree. C.), scale
divisions at X revolutions per minute Polymer Concentration
Revolutions per minute (rpm) API fluid No. % by wt. 600 300 200 100
6 3 loss mL 1 (C) 0.25 167 91 63 34 5 3.5 130 1 (C) 0.5 >300 168
117 64 7.5 5.0 52 4 (P) 0.25 170 91 63 34 5 3.5 80 4 (P) 0.5
>300 174 119 65 7 4.5 42 2 (P) 0.5 295 164 113 62 7 4.5 44 4 (P)
0.5 >300 174 119 65 7 4.5 42 13 (P) 0.5 >300 179 126 70 8 5
40 7 (P) 0.5 >300 174 123 68 7 4 43 31 (P) 0.5 >300 167 121
58 7.5 3.5 54 26 (P) 0.5 295 173 119 64 7 4.5 60 (P) = inventive
polymer (ex.: 30 (P) = inventive polymer 30 from Table 1a))
[0175] Table 5 shows the water loss-reducing properties of selected
abovementioned mixture of starch and the polymers of the invention
according to API spec. 10 under various temperature conditions
(250.degree. F., 300.degree. F. and 350.degree. F.) in a stirred
filtration test in the Fann HTHP filter press (stirring fluid loss
apparatus, SFLA).
[0176] Formulation of the cement slurries:
[0177] 100 g of Dyckerhoff Class G Cement
[0178] 35 g of silica flour
[0179] 54.8 g of distilled water
[0180] Polymer in the concentration specified in table 3 or 4
[0181] 0.3 g of dispersant (polynaphthalenesulfonate, PNS) 0.5-1.5
g of retarder (lignosulfonate)
TABLE-US-00013 TABLE 5 (Use tests of the mixtures at different
temperatures) Rheology after mixing at 75.degree. F. (24.degree.
C.), scale divisions at X revolutions per minute Polymer
Revolutions per minute (rpm) API fluid No. Temp. .degree. F. 600
300 200 100 6 3 loss mL 2 250 188 104 71 38 5 4 102 4 250 173 93 63
34 6 5 106 3 250 208 115 79 43 6 4.5 60 2 300 191 108 74 42 8.5 9
52 4 300 203 113 78 43 7.5 6.5 46 3 300 242 133 94 52 9 7.5 43 3
300 228 127 88 49 9 7.5 41 2 350 206 119 91 50 15 14 96 3 350 217
123 89 54 13.5 12.5 92 (P) = inventive polymer (ex.: 30 (P) =
inventive polymer 30 from table 1a))
[0182] It was therefore an object of the present invention to
provide polymers which can help to achieve improved control of
liquid loss in the cement slurries for cementing wellbores at
temperatures between 80.degree. F. and 300.degree. F. WO-99/26991
describes copolymers of AMPS and acrylamide. Table 4 on page 23
discloses that there is a distinct decline in the water
loss-reducing properties of the polymers described within a
temperature range between 100.degree. F. and 200.degree. F., and
doubling of the water loss in some cases in the use test. The
addition of acrylic acid in the polymers of the invention
distinctly improves the water loss compared to the polymers of
WO-99/26991. The comparative examples which follow are intended to
demonstrate this.
[0183] Comparative examples according to WO-99/26991:
Comparative Polymer 7: (not in accordance with the invention,
prepared according to WO-99/26991--copolymer of
acryloyldimethyltaurate 70% by weight and acrylamide 30% by
weight)
[0184] In a 3 liter Quickfit flask with anchor stirrer, reflux
condenser with offgas scrubber, combined thermometer/pH meter and a
gas inlet tube, 50 ml of distilled water are added to 1700 g of
anhydrous 2-methylpropan-2-ol. The reaction vessel is in a
thermostated heating bath.
[0185] This reaction vessel is blanketed with nitrogen gas and, in
a gentle nitrogen countercurrent, 245 g of acryloyldimethyltaurate
are introduced. The acryloyldimethyltaurate does not dissolve
completely in the 2-methylpropan-2-ol/water mixture and is partly
in the form of a dispersion of solids. The pH of this mixture is
below pH 1. Gaseous ammonia is introduced through the gas inlet
tube above the liquid phase until the pH of the dispersion is
between 7 and 8. On attainment of the desired pH, the mixture is
stirred for a further 1 hour and the pH is recorded continuously.
The reaction vessel is blanketed with nitrogen, and 105 g of
acrylamide are introduced. After the acrylamide has been
introduced, the pH is checked again and, if necessary, corrected to
the range of pH 7 to 8. A constant nitrogen stream is passed
through the solution for at least 1 hour. After this inertization
period, the residual oxygen level is checked by means of an oxygen
electrode. Should the residual oxygen value in the liquid phase
exceed the value of 1 ppm, another inertization is necessary until
this value is attained. Thereafter, in a gentle nitrogen stream,
1.5 g of AIBN are added and the reaction vessel is heated to
60.degree. C. Shortly after the attainment of an internal
temperature of 60.degree. C., the introduction of nitrogen gas is
ended and commencement of the polymerization reaction is observed,
which can be identified by an increase in temperature of 10 to
15.degree. C. About 5-15 minutes after onset of the polymerization
reaction, the temperature maximum has been exceeded and the
temperature in the reaction vessel is increased by the heating bath
up to the boiling point of the 2-methylpropan-2-ol/water mixture.
Under gentle reflux, the now viscous mass is stirred for a further
two hours. The reaction product, in the form of a viscous
suspension of polymer in the 2-methylpropan-2-ol/water mixture, is
separated off by filtration and subsequent drying in a vacuum
drying cabinet.
[0186] Yield: 362 g
[0187] Dry content (IR drier, 15 minutes at 120.degree. C.):
97.5%
[0188] K value (0.5% solution in distilled water): 208
Comparative Polymer 8 (not in accordance with the invention,
prepared according to WO-99/26991 copolymer of
acryloyldimethyltaurate 60% by weight and acrylamide 40% by
weight)
[0189] The comparative example is prepared analogously to
comparative polymer 7. Rather than the amounts specified in
comparative polymer 7, 210 g of acryloyldimethyltaurate and 140 g
of acrylamide are used.
[0190] Yield: 371 g
[0191] Dry content (IR drier, 15 minutes at 120.degree. C.):
95.5%
[0192] K value (0.5% solution in distilled water): 219
Comparative Polymer 9 (not in accordance with the invention,
prepared according to WO-99/26991 copolymer of
acryloyldimethyltaurate 60% by weight and acrylamide 40% by
weight)
[0193] The comparative example is prepared analogously to
comparative polymer 7. Rather than the amounts specified in
comparative polymer 7, 280 g of acryloyldimethyltaurate and 70 g of
acrylamide are used.
[0194] Yield: 363 g
[0195] Dry content (IR drier, 15 minutes at 120.degree. C.):
96%
[0196] K value (0.5% solution in distilled water): 201
Examples of Test Results
[0197] Testing is effected according to API spec. 10. In an
atmospheric consistometer, the cement slurry is stirred/conditioned
at analysis temperature and then, at the same temperature, the
rheology is measured with the FANN model 35SA viscometer (at high
temperature, conditioning is effected at 93.degree. C. and the
viscosity is measured) and the water loss is measured at below
120.degree. C. with a Baroid HTHP filter press and at above
120.degree. C. with the stirring fluid loss test apparatus. The
setting times were determined with an Autoclave Engineers HTHP
consistometer. Formulation of the cement slurries: ad 100%
Dyckerhoff Class G Cement, 43.7% distilled water, 0.3% polymer.
[0198] Table 6 shows the water loss-reducing properties of selected
abovementioned examples according to API spec. 10 at 35.degree. C.
(95.degree. F.) in a static filtration test in the Baroid HTHP
filter press. This makes it clear that it was possible with the
polymers of the invention to considerably improve the reduction in
water loss at low temperatures compared to the comparative
examples. Comparative example 7 differs from comparative example 1
merely by a somewhat smaller amount of initiator (1.5 g rather than
2.0); the measured K value for both polymers mentioned is identical
to the value reported in WO-99/26991 and is 212. Both polymers were
synthesized by the same method as a precipitation polymer in
tert-BuOH.
TABLE-US-00014 TABLE 6 API spec. 10 at 35.degree. C. (95.degree.
F.) of the polymers of the invention compared to comparative
examples 1 and 6 to 8 Rheology after mixing at 75.degree. F.
(24.degree. C.), scale divisions at X revolutions per minute
Polymer Concentration Revolutions per minute/rpm API fluid No. % by
wt. 600 300 200 100 6 3 loss mL 2 (P) 0.5 95 74 46 33 6 3 60 4 (P)
0.3 108 77 44 30 5 3.5 58 8 (P) 0.3 103 73 39 28 4 3 72 13 (P) 0.3
90 72 38 25 4 3 75 20 (P) 0.5 88 67 47 28 4.5 3.5 66 28 (P) 0.3 87
69 39 26 5 3 65 33 (P) 0.3 98 82 59 30 6 3.5 70 36 (P) 0.3 86 63 42
30 5 3.5 68 1 (C) 0.3 94 68 39 26 5 3 115 7 (C) 0.3 96 72 41 26 4.5
3.5 109 8 (C) 0.3 113 81 47 29 6 3 121 9 (C) 0.3 87 75 54 33 6 4
116 (P) = polymer (C) = comparative example
TABLE-US-00015 TABLE 7 API spec. 10 at 250.degree. F.
(121.1.degree. C.) of the polymers of the invention compared to
comparative examples 1 and 6 to 8 Rheology after mixing at
75.degree. F. (24.degree. C.), scale divisions at X revolutions per
minute Polymer Concentration Revolutions per minute/rpm API fluid
No. % by wt. 600 300 200 100 6 3 loss mL 4 (P) 0.5 >300 174 119
65 7 4.5 42 2 (P) 0.5 295 164 113 62 7 4.5 44 13 (P) 0.5 >300
179 126 70 8 5 40 7 (P) 0.5 >300 174 123 68 7 4 43 31 (P) 0.5
>300 167 121 58 7.5 3.5 54 1 (C) 0.5 >300 168 117 64 7.5 5.0
52 7 (C) 0.5 >300 175 113 67 7 5 54 8 (C) 0.5 >300 187 129 72
8 6 60 9 (C) 0.5 >300 159 110 63 7 4.5 58 (P) = polymer (C) =
comparative example
[0199] In table 6, it was possible to detect an improvement in the
water loss-reducing properties at 95.degree. F. The water
loss-reducing properties of comparative example 7 by direct
comparison with comparative example 1 show nearly identical values
and demonstrate the reproducibility of the process used.
Nevertheless, the water loss of comparative polymers 1 and 6 to 9
at an average of 115 mL +/-5 mL is distinctly higher than that of
the polymers of the invention. The difference in the water loss of
the polymers of the invention relative to the comparative polymers
was between 30 and 55 mL. This demonstrates clearly that the
addition of acrylic acid leads to a technical improvement at low
temperatures.
[0200] Table 7 shows the water loss-reducing properties of selected
abovementioned examples according to API spec. 10 at 250.degree. F.
(121.1.degree. C.) in a static filtration test in the Baroid HTHP
filter press. In this test too, it was possible to show that the
polymers of the invention have a demonstrably lower water loss at
temperatures between 80.degree. F. and 300.degree. F. and under
identical experimental conditions than the polymers of WO-99/26991.
Running the comparison between comparative example 7 of WO-99/26991
and comparative example 1 (according to EP 1045869) again, the good
reproducibility of the process used is shown in this test as well.
The use tests conducted according to API spec. 10 at 95.degree. F.
and 250.degree. F. demonstrate clearly that addition of acrylic
acid to the polymers of the invention leads to an improvement in
the water loss-reducing properties.
* * * * *